1. FIELD OF THE INVENTION
The present invention relates to a reading and writing device for use in reading and writing information in an IC card.
2. DESCRIPTION OF THE PRIOR ART
There have been used vending machines which sell goods by use of a card, without the payment of money. As commercially available cards, there are various kinds such as magnetic cards in which a magnetic sheet is installed or IC cards having a data processing unit in the form of an integrated circuit. However, the memory capacity of magnetic card is not so large and the memory capacity of a conventional IC card using RAM (random access memory) is limited by a power supply used in the IC card.
In order to increase the memory capacity of the IC card, the present inventors have proposed an IC card using a PROM (programmable read only memory). In the proposed IC card, a battery is unnecessary for maintaining the data in the PROM, whereby the capacity of the memory can be increased.
FIG. 1 shows one example of the proposed IC card, where 1 denotes the body of, 2 denotes a circuit board, 3-1 to 3-8 denote external connecting terminals for a power supply, data input and output, clock input and ground. 4 denotes a data processor, and 5 denotes a PROM for storing data.
As shown in FIG. 1, in the proposed IC card, there is a recess in which the circuit board having the data processor 4 and IC PROM is embedded. The external terminals 3-1 to 3-8 are formed on the circuit board 2 so that the external terminals are exposed 1 for connection with an external circuit arrangement. When the proposed IC card is inserted in a card reader and writer (not shown), the circuits in the IC card and the card reader and writer are coupled through the external terminals 3-1 to 3-8 so as to couple the data processor 4 with a host computer connected to the card reader and writer.
The PROM 5 is used for storing data and the data processor 4 processes the data from the card reader and writer or from PROM 5 based on the program stored in the data processor 4.
The circuit arrangement of the IC card is shown in FIG. 2 in which 6 denotes a program memory, 7 denotes CPU, 8 denotes an address decoder, 9 denotes a data bus and 10 denotes an address bus. The program memory 6 stores a processing program and CPU 7 operates to write in and read out the data stored in PROM 5 upon execution of the process program from the program memory 6 by accessing sequentially the addresses of the program memory 6 through the address bus 10 and the address decoder 8. For writing the data in the IC card, data supplied from the card reader and writer through the data bus 9 can be written in a predetermined address of PROM 5 designated by the address signal fed from the CPU 7 through the address bus 10 and the address decoder 8. For reading the data, a predetermined address of PROM 5 is designated by CPU 7 through the address bus 10 and address decoder 8 and the data read out from the designated address of PROM 5 is sent to the host computer through the data bus 9.
As the PROM which is a non-volatile memory, EPROM , EEPROM and fuse ROM are used. These ROMs are respectively different in driving characteristics. The conventional card reader and writer is operable for only one type of driving conditions, therefore, a conventional card reader and writer can not be used for the various types of PROMs. For example, the card reader and writer designed for a card using the EPROM requires a power source for supplying +21 volt of write-in voltage. The card reader and writer for a card using EEPROM requires a power supply for generating +5 volt write-in voltage. In case an IC card of which the write-in voltage is not compatible is inserted in one card reader and writer, erroneous data may be written in the memory and in the worst case, PROM 5 may be damaged. Thus, in order to make the IC cards practical for use, it is essential to provide a card reader and writer which is compatible to various IC cards having different drive conditions.